The experimental work proposed is designed to investigate various aspects of metabolic behavior of normal and pathologic articular cartilage by histologic, ultrastructural, histochemical, autoradiographic, biochemical, and metabolic (radioisotopic) techniques. Experiments will be performed to assess the metabolic activity of articular chondrocytes in normal and osteoarthritic tissue and in a matrix-free preparation. This tissue will be studied to determine the content of degradative enzymes with a special emphasis on collagenase and a neutral proteoglycanase. Studies will attempt to define the role of uridine diphosphate as a stimulator of proteoglycan synthesis in normal, lacerated and experimentally arthritic articular tissue and also the effect of low dose papain treatment on cartilage wound healing and the action of synovial extracts culture fluid on articular cartilage metabolism. Studies will be directed at improved preservation of articular cartilage for use as allografts. Patients who have received allografts for malignant bone tumors will be studied for presence of humoral and cytotoxic antibodies and an animal model for articular cartilage allograft transplantation will be devised and subjected to immunological evaluation. The effect of pressure on chondrocyte metabolism will be further elucidated.